The disclosure proceeds from a device for determining motion parameters.
In order to measure rotational speeds, positions or else linear motions, frequent use is made nowadays of a magnetic multipole whose magnetic field is then measured with the aid of a magnetic sensor. The multipole can be used in the form of a wheel (multipole wheel) or as a linear scale (graduated scale). Such multipoles are available in the form of adhesive tapes or on magnetized components. The magnetic field is mostly measured with the aid of Hall, AMR or GMR sensors. An approximately sinusoidal output signal is obtained therefrom. It is therefore possible to further subdivide the scale provided by the multipole, and to specify the position even in the case of intermediate values. That is helpful for an accurate measurement, but unnecessary for measuring only the rotational speed. More cost-effective concepts would be advantageous here. A further disadvantage of these concepts is that all the sensors exhibit a clear temperature influence with reference to the signal (TKE and TKO) and, moreover, can no longer be used at temperatures above 150-200° C.
A simpler and more cost-effective concept is to use a simple coil to determine the rotational speed. Said coil measures, as an induced voltage, the field changes occurring because of the in the case of rotation or linear movement. However, in this case a sufficiently fast motion of the multipole is required, since the induced voltage is a function of the speed of the field change dB/dt. This principle fails in the case of slow motions. In return, simple coils can be used even in the case of high temperatures; the signal itself is completely independent of temperature.
By way of example, a device for contactless detection of linear or rotational motions is described in Laid-open patent application DE 10 2007 023 385 A1. The device described operates with a fixed magnetoresistive chip sensor and a magnetic field transmitter device which is adjacent to said chip sensor while leaving free an air gap and whose individual magnetic segments are alternately substantially magnetized in terms of their polarity in a direction of a three-dimensional coordinate system. The chip sensor is arranged with its large surfaces substantially perpendicular or parallel, or at an arbitrary angular position therebetween, in relation to the surface of the multipole arrangement.
The older patent application DE 10 2009 001 395.4 in the name of the applicant discloses a device for measuring a magnetic field which comprises an exciter coil and a magnetizable core material. The core material has a first Weiss domain and a second Weiss domain, the first Weiss domain and the second Weiss domain adjoining a common Bloch wall. In order to measure a magnetic field, an alternating voltage is applied to the exciter coil with the formation of a periodically alternating magnetic field, the result being that the core material is periodically remagnetized. The magnetic field to be measured and the magnetic field of the exciter coil overlap one another, the result being a temporal shift in the remagnetization of the core material. The magnetic field to be measured can be deduced from the temporal shift in the remagnetization of the core material. In addition, the device has a measuring coil for measuring the change in the magnetic field of the core material, the time of the remagnetization being determined by a change in voltage induced in the measuring coil, in particular a voltage pulse.